Places you do not want to visit

1. Linfen, China

A number of Chinese cities could've made this list for the same reason - pollution - but Linfen takes the cake because it has the dirtiest air in the entire world.

A small city (pop. 4,000,000 - yes, that's a small city in China) located in southern Shanxi province, Linfen's air pollution problem is legendary, a result of being one of China's largest coal mining hubs. The air is filled with soot and pollutants and water is contaminated by arsenic. There is a heightened risk of bronchitis, pneumonia, and lung cancer for residents.

The entire Shanxi province, a hard-scrabble region on China's western central plains, is plagued by air pollution. Shanxi has 270 billion tons of proven coal reserves, and coal is everywhere - piled in back alleys and sold in burnable cubes. Until China's government makes a more sincere effort at cleaning up the environment, the sun won't be shining in Linfen for sometime to come.

2. Ciudad Juarez, Mexico

Pervasive, shocking violence has catapulted Ciudad Juarez to the world’s attention and forced the Mexican military to intervene to shore up security. Whether these troops will be effective, or whether they’ll be subsumed in the wave of kidnappings, torture and rampant corruption and intimidation is a key concern to the U.S., as Ciudad Juarez is just across the border from El Paso, Texas.

The city of 1.5 million has already experienced 1,800 murders since January, 2010 and is the epicenter of a violent battle between rival drug cartels, smugglers, kidnappers and criminals. Among the city's grim statistics, over 400 women have fallen prey to "sexual homicide" since 1999. Dismembered bodies and large "common graves" stuffed with corpses have inspired the CIA and Pentagon to begin contingency planning for a “failed state” on America’s southern border.

3. Norilsk, Russia

What is it like in the city of 134,000 in Siberia, Russia?

Time Magazine states that "Norilsk was founded in 1935 as a Siberian slave labor camp, and life there has pretty much gone downhill since."

Norilsk is home to the world's largest heavy metal smelting complex, with little or no regulartory oversight. Polluted water and air make life expectancy in this city around just 40 years. Within 30 miles of the city, there is not a single living tree.

And it's pretty darn cold. Norilsk is the northernmost city on the planet with a population over 100,000. Average temperature is about 14 degrees Fahrenheit (-10 Celcius). The city is covered with snow for about 250-270 days a year, with snow storms for about 110-130 days. Other than that, it's really balmy up there. Just in case you're thinking about visiting - the city has been closed to foreigners since 2001.

4. Mogadishu, Somalia

The capital of Somalia is nearly synonymous with chaos and violence. Seared into the American consciousness with the 1993 "Battle of Mogadishu," which claimed the lives of 19 servicemen and memorialized by the book "Black Hawk Down," Mogadishu has been wracked with internal unrest ever since.

The city received renewed international attention when the Islamic Courts Union claimed control over the city, only to be pushed back by Ethiopian forces. In 2010, while nominally governed by the UN-sanctioned Transitional Federal Government and policed by forces from the African Union, Mogadshu remains the scene of running gun battles between rival militias and tribal factions, as well as Islamic insurgents seeking to eject AU forces.

Hundreds of lives are lost each day to fighting among Islamist groups as well as fighting among Islamist and Christians. Over a million of the city's residents have reportedly been displaced, with tens of thousands fleeing the "city of death" altogether.

And this city is the nominal capital of a Country who host the modern day "Pirates" who ply upon shipping along the East African Coast.